Small Diameter 347 Stainless Steel Tube
347 Stainless Steel (also known as EN 1.4546.9 or UNS S34700 steel) is a special alloy in the 300 series austenitic family and specifically a close cousin to SS321’s performance characteristics. Compared to 304 ss tubing, it contains similar percentages of of Chromium and Nickel, iron and other alloying elements, but the addition of two elements (tantalum and niobium) play a crucial role in the performance of this alloy. Although they comprise a tiny percentage of the melt by weight, these elements give 347 SS tubing greater protection from carbide precipitation in the HAZ (or heat affected zone) of the welded tube, and provide greater protection from intergranular corrosion relative to 304 or 316 tubing options. Niobium (sometimes called Columbium) and tantalum attract carbon more readily than chromium. Essentially, these critical elements reduce the percent of carbon binding with chromium at the weld zone, which equates to reduced chromium carbide precipitation.
347 Small Diameter Stainless Steel Tubing
The occurrence of carbide precipitation reduces the percent of available chromium that can bind with oxygen at the surface level to form the invisible magic boundary layer called chromium oxide. This invisible layer, only atomic deep, is what gives all stainless steels the property of remaining largely bright and shiny in the presence of moisture, air and corrosive solutions that would otherwise rapidly break down the metal.
Attacks from corrosive solutions on the weld zone and base metal occur more quickly as temperatures and acid concentrations increase (even more so if both increase). Therefore 347 tubing is purposely used in environments where exposures to corrosive, caustic solutions at high temperatures is part of the service life of the tubular product. Stable at high temperatures, 347 tubing can be cold worked to hard tempers like its cousins 304 and 316, delivering mechanical values from annealed to over 160 KPSI ultimate tensile strength.
Industries & Applications:
Frequent uses for 347 SS tubes include heat exchange products, exhaust tubes, aerospace applications and chemical applications.
Vita Needle can weld and draw to size 347 tubing from 5/16" OD and smaller, with minimum runs of 10' to over 100,000'. Tubing is sold in coil, straight lengths or fabricated parts (fabricated via EDM, Mill/turn, grinding or other reductive machining methods). Our unique capabilities to draw and fabricate 347 tubing specific to customer requirements with short deliveries sets Vita apart from peers who may have to subcontract elements of a product build. Please send us your inquiry or questions and we look forward to responding promptly!